The present invention relates to an electronic weight measuring device.
In general, in an electronic weight measuring device, to accurately measure the weight, it is necessary to preliminarily set the zero point and span of this device. Therefore, hitherto, the electronic weight measuring device is provided with a zero point setting key and a span setting key. In the case of setting the zero point, the weight measuring device is put into an unloaded state and the zero-point setting key is operated. In the case of setting the span, the weight measuring device is applied with a rated weight and the span setting key is operated in this state.
FIG. 1 is a flowchart showing the operations to set the zero point and span. When the first key is depressed in the test mode set by the mode setting switch, the zero point data is set. When the seccnd key is depressed, the span data is set.
In such a kind of electronic weight measuring device, a count value C1 obtained when the zero point was set and a count value C2 derived when the span was set are stored into a nonvolatile RAM. Span data SD is given as a difference between count values C.sub.1 and C.sub.2 and stored into the nonvolatile RAM. The span coefficient which is calculated from span data SD and a predetermined span count value is also stored into this RAM. In the case of checking the resultant span data to see if it is proper or not, the count value which is derived when a weight of a rated weight was put on the weight measuring device is multiplied with the span coefficient and thereafter, the resultant count value is displayed. Therefore, by merely checking whether the displayed count value coincides with the span count value or not, it is possible to determine whether the span data stored in the nonvolatile RAM is correct or not.
However, in the case of such a conventional method, two keys must be used to set both of the zero point and the span, so that the demand to reduce the size and cost of the electronic weight measuring device cannot be satisfied.